There is a need for improving the erosion resistance of current materials used for long wave infrared transmitting applications such as domes and infrared windows. (Report of the Committee on Mechanical Properties of Infrared Transmitting Materials, Publication NMAB-336, National Academy of Sciences, 1978). A number of materials that transmit infrared (IR) at wavelengths longer than 8 micrometers (halides, sulfides, arsenides, selenides gallium arsenide, III-V and II-VI compounds) generally suffer from weak mechanical durability which limits their usefulness. It has now been found that composites having improved toughness and durability can be fabricated by uniformly dispersing small particles of diamonds in an appropriate matrix.
Diamond films and coatings have many uses including wear resistant parts, semiconductor devices, infrared, and diamond-like windows, electronic applications and radomes. There is on-going need to improve the strength of such films and their integrity against environmental degradation.
Diamond films have been grown on various substrates by vapor deposition methods. U.S. Pat. No. 4,816,286 (Hirose) teaches a method for synthesis of diamond by gas decomposition of an organic compound on the surface of a substrate by heat, electron beam, light, direct current glow discharge, alternating current glow discharge or direct current arc discharge.
Matsumoto et al (Journal of Material Science, 17:3106-3112 (1982)) grew microcrystals of diamond on silicon, molybdenum and silica substrates by vapor chemical deposition of hydrocarbon/hydrogen mixtures with a hot tungsten filament. As recited in that article, other methods of preparing chemical films include ion-beam deposition, sputtering, and plasma CVD. Matsumoto, S. (J. Materials Science Letters, 4:600-602 (1985)) described a RF discharge activation method for depositing diamond microcrystals or silicon wafers, molybdenum and silica-glass plates using a hydrogen/methane mixture.
Sawabe et al (Thin Solid Film, 137:89-99 (1986)) grew tin diamond films on silicon and SiC by electron-assisted chemical vapor deposition (EACUD). The growth of diamond films on these substrates is believed to be limited by the nucleation of diamond crystals. For example, it is now well recognized that the growth of the diamond films is enhanced by the presence of diamond particles that are left behind on the surface of silicon wafers when the wafers are polished with diamond paste (Okano et al, Japanese Journal of Applied Physics, 27(2):1173-1175 (1988)); these particles of diamond serve as the nuclei for the growth of the diamond films.
The present invention relates to infrared transmitting diamond composites, their preparation and to improved diamond or diamond-like coatings.